Against the backdrop of global energy shortages and increasingly severe environmental pollution,renewable energy is gradually becoming a significant direction for future energy development.Power electronics converters...Against the backdrop of global energy shortages and increasingly severe environmental pollution,renewable energy is gradually becoming a significant direction for future energy development.Power electronics converters,as the core technology for energy conversion and control,play a crucial role in enhancing the efficiency and stability of renewable energy systems.This paper explores the basic principles and functions of power electronics converters and their specific applications in photovoltaic power generation,wind power generation,and energy storage systems.Additionally,it analyzes the current innovations in high-efficiency energy conversion,multilevel conversion technology,and the application of new materials and devices.By studying these technologies,the aim is to promote the widespread application of power electronics converters in renewable energy systems and provide theoretical and technical support for achieving sustainable energy development.展开更多
We demonstrate superb large-area verticalβ-Ga_(2)O_(3)SBDs with a Schottky contact area of 1×1 mm^(2)and obtain a high-efficiency DC-DC converter based on the device.Theβ-Ga_(2)O_(3)SBD can obtain a forward cur...We demonstrate superb large-area verticalβ-Ga_(2)O_(3)SBDs with a Schottky contact area of 1×1 mm^(2)and obtain a high-efficiency DC-DC converter based on the device.Theβ-Ga_(2)O_(3)SBD can obtain a forward current of 8 A with a forward volt-age of 5 V,and has a reverse breakdown voltage of 612 V.The forward turn-on voltage(VF)and the on-resistance(Ron)are 1.17 V and 0.46Ω,respectively.The conversion efficiency of theβ-Ga_(2)O_(3)SBD-based DC-DC converter is 95.81%.This work indicates the great potential of Ga_(2)O_(3)SBDs and relevant circuits in power electronic applications.展开更多
Thermal energy,i.e.,the electromagnetic energy in the infrared range that originates from the direct solar radiation,outgoing terrestrial radiation,waste heat from combustion of fuels,heat-emitting electrical devices,...Thermal energy,i.e.,the electromagnetic energy in the infrared range that originates from the direct solar radiation,outgoing terrestrial radiation,waste heat from combustion of fuels,heat-emitting electrical devices,decay of radioactive isotopes,organic putrefaction and fermentation,human body heat,and so on,constitutes a huge energy flux circulating on the earth surface.However,most energy converters designed for the conversion of electromagnetic energy into electricity,such as photovoltaic cells,are mainly focused on using a narrow part of the solar energy lying in the visible spectrum,while thermomechanical engines that are fueled by heat in the broad energy range and then convert it into mechanical work or store it as mechanical deformation,are paid less attention.Although the efficiency of thermomechanical devices is relatively low,they can be applied to collect waste heat which otherwise contributes to negative climate changes.In this review,operational principles of thermomechanical energy converters and a description of basic devices and materials that utilize thermal energy are given.In addition to conventional macroscopic engines,based on thermoacoustic,thermomagnetic,thermoelastic,hydride heat converters,and shape memory alloys,the emergent devices are described which are classified as smart actuators,breathing frameworks,thermoacoustic micro-transducers,nanomechanical resonators,plasmomechanical systems,and optothermal walkers.The performance of the different types of thermomechanical energy converters is described and compared.展开更多
Lead is a ubiquitous pollutant and Pb pollution is a global public health problem.Lead has been reported to induce multiple adverse effects,including reproductive toxicity,neurotoxicity,carcinogenicity,nephrotoxicity,...Lead is a ubiquitous pollutant and Pb pollution is a global public health problem.Lead has been reported to induce multiple adverse effects,including reproductive toxicity,neurotoxicity,carcinogenicity,nephrotoxicity,immunotoxicity,and hypertension[1].The traditional medical treatment available for Pb poisoning is chelation,which can save lives in individuals with very high blood Pb levels.The commonly used chelating agents include CaNa2EDTA and meso-2,3-dimercaptosuccinic acid.However,chelation therapy has strong short-term effects on the overall long-term management of Pb exposure.展开更多
Switched-capacitor(SC)DC-DC converter[1]is an impor-tant alternative to inductive DC-DC converter,in terms of removing the bulky power inductor.Hence,it is widely used in low-profile,low-power applications,such as the...Switched-capacitor(SC)DC-DC converter[1]is an impor-tant alternative to inductive DC-DC converter,in terms of removing the bulky power inductor.Hence,it is widely used in low-profile,low-power applications,such as the internet of things(IoT)sensor nodes and energy harvesting[2].Mean-while,considering that capacitor has a much higher energy density than inductor,high-power applications.展开更多
Code converters are essential in digital nano communication;therefore,a low-complexity optimal QCA layout for a BCD to Excess-3 code converter has been proposed in this paper.A QCA clockphase-based design technique wa...Code converters are essential in digital nano communication;therefore,a low-complexity optimal QCA layout for a BCD to Excess-3 code converter has been proposed in this paper.A QCA clockphase-based design technique was adopted to investigate integration with other complicated circuits.Using a unique XOR gate,the recommended circuit’s cell complexity has been decreased.The findings produced using the QCADesigner-2.0.3,a reliable simulation tool,prove the effectiveness of the current structure over earlier designs by considering the number of cells deployed,the area occupied,and the latency as design metrics.In addition,the popular tool QCAPro was used to estimate the energy dissipation of the proposed design.The proposed technique reduces the occupied space by∼40%,improves cell complexity by∼20%,and reduces energy dissipation by∼1.8 times(atγ=1.5EK)compared to the current scalable designs.This paper also studied the suggested structure’s energy dissipation and compared it to existing works for a better performance evaluation.展开更多
Optical mode converters are essential for enhancing the capacity of optical communication systems. However, fabrication errors restrict the further improvement of conventional mode converters. To address this challeng...Optical mode converters are essential for enhancing the capacity of optical communication systems. However, fabrication errors restrict the further improvement of conventional mode converters. To address this challenge, we have designed an on-chip TE0–TE1mode converter based on topologically protected waveguide arrays. The simulation results demonstrate that the converter exhibits a mode coupling efficiency of 93.5% near 1550 nm and can tolerate a relative fabrication error of 30%. Our design approach can be extended to enhance the robustness for other integrated photonic devices, beneficial for future development of optical network systems.展开更多
Extracellular vesicles(EVs)are membranous vesicular structures released from almost all eukaryotic cell types under different physiological or pathological conditions.Growing evidence demonstrates that EVs can serve a...Extracellular vesicles(EVs)are membranous vesicular structures released from almost all eukaryotic cell types under different physiological or pathological conditions.Growing evidence demonstrates that EVs can serve as mediators of intercellular communication between donor and recipient cells or microorganism-infected and noninfected cells.Coronavirus disease 2019(COVID-19)disease is caused by infection of the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)of host cells in the respiratory system and various extra-pulmonary tissue/organs,resulting in complications of multiple organ systems.As the cell surface receptor,angiotensin-converting enzyme 2(ACE2)mediates cellular entry of SARS-CoV-2 into the host cells in patients with COVID-19.Recent studies have found that ACE2 can be released with EVs,which have been shown to interfere with the entry of the virus into host cells and thus may be involved in COVID-19 pathophysiology.In addition,ACE2,neprilysin(NEP),and thimet oligopeptidase(TOP)are the key enzymes that regulate angiotensin metabolism by converting angiotensin II or angiotensin I to angiotensin 1-7,the latter of which has protective effects in counterbalancing the harmful effects of angiotensin II in COVID-19 disease.This review summarizes the recent research progress regarding EV-associated ACE2,NEP,and TOP and the perspectives of their potential involvement in the pathophysiology of COVID-19 disease.展开更多
In recent years,switched inductor(SL)technology,switched capacitor(SC)technology,and switched inductor-capacitor(SL-SC)technology have been widely applied to optimize and improve DC-DC boost converters,which can effec...In recent years,switched inductor(SL)technology,switched capacitor(SC)technology,and switched inductor-capacitor(SL-SC)technology have been widely applied to optimize and improve DC-DC boost converters,which can effectively enhance voltage gain and reduce device stress.To address the issue of low output voltage in current renewable energy power generation systems,this study proposes a novel non-isolated cubic high-gain DC-DC converter based on the traditional quadratic DC-DC boost converter by incorporating a SC and a SL-SC unit.Firstly,the proposed converter’s details are elaborated,including its topology structure,operating mode,voltage gain,device stress,and power loss.Subsequently,a comparative analysis is conducted on the voltage gain and device stress between the proposed converter and other high-gain converters.Then,a closed-loop simulation system is constructed to obtain simulation waveforms of various devices and explore the dynamic performance.Finally,an experimental prototype is built,experimental waveforms are obtained,and the experimental dynamic performance and conversion efficiency are analyzed.The theoretical analysis’s correctness is verified through simulation and experimental results.The proposed converter has advantages such as high voltage gain,low device stress,high conversion efficiency,simple control,and wide input voltage range,achieving a good balance between voltage gain,device stress,and power loss.The proposed converter is well-suited for renewable energy systems and holds theoretical significance and practical value in renewable energy applications.It provides an effective solution to the issue of low output voltage in renewable energy power generation systems.展开更多
In the DC microgrid,the lack of inertia and damping in power electronic converters results in poor stability of DC bus voltage and low inertia of the DC microgrid during fluctuations in load and photovoltaic power.To ...In the DC microgrid,the lack of inertia and damping in power electronic converters results in poor stability of DC bus voltage and low inertia of the DC microgrid during fluctuations in load and photovoltaic power.To address this issue,the application of a virtual synchronous generator(VSG)in grid-connected inverters control is referenced and proposes a control strategy called the analogous virtual synchronous generator(AVSG)control strategy for the interface DC/DC converter of the battery in the microgrid.Besides,a flexible parameter adaptive control method is introduced to further enhance the inertial behavior of the AVSG control.Firstly,a theoretical analysis is conducted on the various components of the DC microgrid,the structure of analogous virtual synchronous generator,and the control structure’s main parameters related to the DC microgrid’s inertial behavior.Secondly,the voltage change rate tracking coefficient is introduced to adjust the change of the virtual capacitance and damping coefficient flexibility,which further strengthens the inertia trend of the DC microgrid.Additionally,a small-signal modeling approach is used to analyze the approximate range of the AVSG’s main parameters ensuring system stability.Finally,conduct a simulation analysis by building the model of the DC microgrid system with photovoltaic(PV)and battery energy storage(BES)in MATLAB/Simulink.Simulation results from different scenarios have verified that the AVSG control introduces fixed inertia and damping into the droop control of the battery,resulting in a certain level of inertia enhancement.Furthermore,the additional adaptive control strategy built upon the AVSG control provides better and flexible inertial support for the DC microgrid,further enhances the stability of the DC bus voltage,and has a more positive impact on the battery performance.展开更多
In order to predict bifurcation point of the closed-loop current-programmed boost converter and enable this converter to operate at stable parameter space, this paper firstly establishes stroboscopic maps for this con...In order to predict bifurcation point of the closed-loop current-programmed boost converter and enable this converter to operate at stable parameter space, this paper firstly establishes stroboscopic maps for this converter in the continuous conduction mode according to operating characteristics and topple of this converter. Parameter space at the steady state and bifurcation types are analysed together with stability theory of nonlinear equation. In the solving course, the duty cycle is avoided because of inversive solution, and accuracy is increased. Finally, correction is proved by numerical calculation.展开更多
This paper shows DC and small-signal circuit models for the PWM DC to DC buck, boost and back/ boost converters with the equivalent series resistance of the inductor. The DC voltage transfer function and the efficienc...This paper shows DC and small-signal circuit models for the PWM DC to DC buck, boost and back/ boost converters with the equivalent series resistance of the inductor. The DC voltage transfer function and the efficiency of the converter are derived from the DC model. Small-signal open-loop characteristics are derived from the small-signal model based on a state variable model. A design example proves the performance of the circuit and verification of the model.展开更多
Automotive torque converters have recently been designed with an increasingly narrower profile for the purpose of achieving a smaller axial size and reducing weight. Design of experiment(DOE) and computational fluid d...Automotive torque converters have recently been designed with an increasingly narrower profile for the purpose of achieving a smaller axial size and reducing weight. Design of experiment(DOE) and computational fluid dynamics(CFD) techniques are applied to improve the performance of a flat torque converter. Four torque converters with different flatness ratios(0.204, 0.186, 0.172, and 0.158) are designed and simulated first to investigate the effects of flatness ratio on their overall performance, including efficiency, torque ratio, and impeller torque factor. The simulation results show that the overall performance tends to deteriorate as the flatness ratio decreases. Then a parametric study covering six geometric parameters, namely, inlet and outlet angles of impeller, turbine, and stator is carried out. The results demonstrate that the inlet and outlet angles play an important role in determining the performance characteristics of a torque converter. Furthermore, the relative importance of the six design parameters is investigated using DOE method for each response(stall torque ratio and peak efficiency). The turbine outlet angle is found to exert the greatest influence on both responses. After DOE analysis, an optimized design for the flat torque converter geometry is obtained. Compared to the conventional product, the width of the optimized flat torque converter torus is reduced by about 20% while the values of stall torque ratio and peak efficiency are only decreased by 0.4% and 1.7%, respectively.The proposed new optimization strategy based on DOE method together with desirability function approach can be used for performance enhancement in the design process of flat torque converters.展开更多
In this paper, period-doubling bifurcation in a two-stage power factor correction converter is analyzed by using the method of incremental harmonic balance (IHB) and Floquet theory. A two-stage power factor correcti...In this paper, period-doubling bifurcation in a two-stage power factor correction converter is analyzed by using the method of incremental harmonic balance (IHB) and Floquet theory. A two-stage power factor correction converter typically employs a cascade configuration of a pre-regulator boost power factor correction converter with average current mode control to achieve a near unity power factor and a tightly regulated post-regulator DC-DC Buck converter with voltage feedback control to regulate the output voltage. Based on the assumption that the tightly regulated postregulator DC-DC Buck converter is represented as a constant power sink and some other assumptions, the simplified model of the two-stage power factor correction converter is derived and its approximate periodic solution is calculated by the method of IHB. And then, the stability of the system is investigated by using Floquet theory and the stable boundaries are presented on the selected parameter spaces. Finally, some experimental results are given to confirm the effectiveness of the theoretical analysis.展开更多
Based on the mechanism for the generation of chaos in a buck converter, a pole placement method is proposed and applied to controlling the chaos in a circuit. The control circuit is designed and tested. Numerical calc...Based on the mechanism for the generation of chaos in a buck converter, a pole placement method is proposed and applied to controlling the chaos in a circuit. The control circuit is designed and tested. Numerical calculation and circuit implementation demonstrate the validity of this chaos control method.展开更多
The so-called Goto's model was modified by introducing a parameter of the oxygen efficiency from industrial trials, as well as the selected and newly re-assessed thermodynamic data. The application of the model to...The so-called Goto's model was modified by introducing a parameter of the oxygen efficiency from industrial trials, as well as the selected and newly re-assessed thermodynamic data. The application of the model to copper converters in Guixi Smelter has been carried out by the combination of thermodynamic calculations with the mass and heat balance using the plant data obtained in industrial trials for many heats. For the slag-making stage, good agreements have been reached betWeen the calculated and measured temperature, blowing time as well as the contents for main elements in the matte and the slag. Relativel}'' large deviations for contents of Zn and Pb in the slag may be caused by the complex chemical composition of the real molten slag, which ma}; result in a large difference of γzn. and γPb,adopted with their real values. It is noted that the model can simulate the slag-making stage of copper converting process in industrial Pierce-Smith converters well.展开更多
The measurements and calculations (coupled mode equations) on the conversion of the transverse magnetic TM_(01) vircator (virtual cathode oscillator) mode at 4 GHz to the linearly polarized TE11 mode are presented by ...The measurements and calculations (coupled mode equations) on the conversion of the transverse magnetic TM_(01) vircator (virtual cathode oscillator) mode at 4 GHz to the linearly polarized TE11 mode are presented by means of mode converter systems using a circular waveguide with curvature. The mode converter is composed of the 38.78°bend with 39.07cm curvature and of the 50.78° inverse bend with 25.24cm curvature in the circular waveguide of 9cm internal diameter. The efficiency of conversion from TM_(01) to TE_(11) at 4 GHz exceeds 90%, and the overall etfficiency from TM_(01) to TE_(11) exceeds 90% in the calculated range from 3.72 to 4.8 GHz.展开更多
This paper makes a review of state-of-the- arts designs of successive-approximation register analog-to-digital converters (SAR ADCs). Methods and technique specifications are collected in view of innovative ideas. A...This paper makes a review of state-of-the- arts designs of successive-approximation register analog-to-digital converters (SAR ADCs). Methods and technique specifications are collected in view of innovative ideas. At the end of this paper, a design example is given to illustrate the procedure to design an SAR ADC. A new method, which extends the width of the internal clock, is also proposed to facilitate different sampling frequencies, which provides more time for the digital-to-analog convert (DAC) and comparator to settle. The 10 bit ADC is simulated in 0.13 μm CMOS process technology. The signal-to-noise and distortion ratio (SNDR) is 54.41 dB at a 10 MHz input with a 50 MS/s sampling rate, and the power is 330 μW.展开更多
With an increasing emphasis on renewable energy resources, wave power technology is becoming one of the realistic solutions. However, the 2011 tsunami in Japan was a harsh reminder of the ferocity of the ocean. It is ...With an increasing emphasis on renewable energy resources, wave power technology is becoming one of the realistic solutions. However, the 2011 tsunami in Japan was a harsh reminder of the ferocity of the ocean. It is known that tsunamis are nearly undetectable in the open ocean but as the wave approaches the shore its energy is compressed, creating large destructive waves. The question posed here is whether an oscillating wave surge converter (OWSC) could withstand the force of an incoming tsunami. Several tools are used to provide an answer: an analytical 3D model developed within the framework of linear theory, a numerical model based on the non-linear shallow water equations and empirical formulas. Numerical results show that run-up and draw-down can be amplified under some circumstances, leading to an OWSC lying on dry ground t展开更多
With application of the lock-up clutch in the torque converter(TC), fuel economy is not much determined by its high-speed ratio transmission efficiency. As a benefit, more researches are focused on its low-speed rat...With application of the lock-up clutch in the torque converter(TC), fuel economy is not much determined by its high-speed ratio transmission efficiency. As a benefit, more researches are focused on its low-speed ratio performance so as to improve vehicle gradeability and launching acceleration performance. According to the results of computational fluid dynamics(CFD) analysis, hydrodynamic loss inside the stator cascade accounts for 42% of the total energy loss at stalling speed ratio. It is found that upstream flow with large impingement angle results in boundary layer separation at the leading edge, which aggregates hydrodynamic loss and decreases circular flow rate dramatically at low-speed ratio. In this paper, a dual-blade stator is proposed to suppress the boundary layer separation, which is parameterized by using the non-uniform rational B spline(NURBS) method. The mean camber line and blade profile curve are expressed by a three control points quadratic open NURBS and a cubic closed one respectively. The key design parameters included the slot width and suction side shape of the primary blade are analyzed. The most effective slot width is found to be between 4% and 8% chord length, and the boundary layer separation can be suppressed completely by decreasing distribution of momentum moment at the primary blade and adding it to the leading edge of the secondary blade. As a result, circular flow rate and impeller torque capacity is increased by 17.9% and 9.6% respectively at stalling speed ratio, meanwhile, low-speed ratio efficiency is also improved. Maximum efficiency at high-speed ratio decreases by 0.5%, which can be ignored as the work of lock-up clutch. This research focuses on using the dual-blade stator to optimize low-speed ratio performance of the TC, which is benefit to vehicle power performance.展开更多
文摘Against the backdrop of global energy shortages and increasingly severe environmental pollution,renewable energy is gradually becoming a significant direction for future energy development.Power electronics converters,as the core technology for energy conversion and control,play a crucial role in enhancing the efficiency and stability of renewable energy systems.This paper explores the basic principles and functions of power electronics converters and their specific applications in photovoltaic power generation,wind power generation,and energy storage systems.Additionally,it analyzes the current innovations in high-efficiency energy conversion,multilevel conversion technology,and the application of new materials and devices.By studying these technologies,the aim is to promote the widespread application of power electronics converters in renewable energy systems and provide theoretical and technical support for achieving sustainable energy development.
基金supported by the National Natural Science Foundation of China (NSFC) under Grant Nos. 61925110, 61821091, 62004184 and 62234007the Key-Area Research and Development Program of Guangdong Province under Grant No. 2020B010174002
文摘We demonstrate superb large-area verticalβ-Ga_(2)O_(3)SBDs with a Schottky contact area of 1×1 mm^(2)and obtain a high-efficiency DC-DC converter based on the device.Theβ-Ga_(2)O_(3)SBD can obtain a forward current of 8 A with a forward volt-age of 5 V,and has a reverse breakdown voltage of 612 V.The forward turn-on voltage(VF)and the on-resistance(Ron)are 1.17 V and 0.46Ω,respectively.The conversion efficiency of theβ-Ga_(2)O_(3)SBD-based DC-DC converter is 95.81%.This work indicates the great potential of Ga_(2)O_(3)SBDs and relevant circuits in power electronic applications.
基金grateful to the Ministry of Education and Sciences of Ukraine(https://mon.gov.ua)for continuing support(Project#М/66-2022).
文摘Thermal energy,i.e.,the electromagnetic energy in the infrared range that originates from the direct solar radiation,outgoing terrestrial radiation,waste heat from combustion of fuels,heat-emitting electrical devices,decay of radioactive isotopes,organic putrefaction and fermentation,human body heat,and so on,constitutes a huge energy flux circulating on the earth surface.However,most energy converters designed for the conversion of electromagnetic energy into electricity,such as photovoltaic cells,are mainly focused on using a narrow part of the solar energy lying in the visible spectrum,while thermomechanical engines that are fueled by heat in the broad energy range and then convert it into mechanical work or store it as mechanical deformation,are paid less attention.Although the efficiency of thermomechanical devices is relatively low,they can be applied to collect waste heat which otherwise contributes to negative climate changes.In this review,operational principles of thermomechanical energy converters and a description of basic devices and materials that utilize thermal energy are given.In addition to conventional macroscopic engines,based on thermoacoustic,thermomagnetic,thermoelastic,hydride heat converters,and shape memory alloys,the emergent devices are described which are classified as smart actuators,breathing frameworks,thermoacoustic micro-transducers,nanomechanical resonators,plasmomechanical systems,and optothermal walkers.The performance of the different types of thermomechanical energy converters is described and compared.
基金sponsored by the Central Government Guides Local Scientific and Technological Development Fund Project(YDZX 20201400001443)Shanxi International Science and Technology Cooperation Project(201803D421065)+2 种基金National Natural Science Foundation of China(Grant No.30672621 and 81173473)Taiyuan City Science and Technology Project Special Talents Star Project(120247-08)Basic Research Project of Shanxi Province(202103021223241).
文摘Lead is a ubiquitous pollutant and Pb pollution is a global public health problem.Lead has been reported to induce multiple adverse effects,including reproductive toxicity,neurotoxicity,carcinogenicity,nephrotoxicity,immunotoxicity,and hypertension[1].The traditional medical treatment available for Pb poisoning is chelation,which can save lives in individuals with very high blood Pb levels.The commonly used chelating agents include CaNa2EDTA and meso-2,3-dimercaptosuccinic acid.However,chelation therapy has strong short-term effects on the overall long-term management of Pb exposure.
基金This work is supported by the Macao Science and Technology Development Fund(FDCT)under Grant 0041/2022/A1by the Research Committee of University of Macao under Grant MYRG2022-00004-IME.
文摘Switched-capacitor(SC)DC-DC converter[1]is an impor-tant alternative to inductive DC-DC converter,in terms of removing the bulky power inductor.Hence,it is widely used in low-profile,low-power applications,such as the internet of things(IoT)sensor nodes and energy harvesting[2].Mean-while,considering that capacitor has a much higher energy density than inductor,high-power applications.
文摘Code converters are essential in digital nano communication;therefore,a low-complexity optimal QCA layout for a BCD to Excess-3 code converter has been proposed in this paper.A QCA clockphase-based design technique was adopted to investigate integration with other complicated circuits.Using a unique XOR gate,the recommended circuit’s cell complexity has been decreased.The findings produced using the QCADesigner-2.0.3,a reliable simulation tool,prove the effectiveness of the current structure over earlier designs by considering the number of cells deployed,the area occupied,and the latency as design metrics.In addition,the popular tool QCAPro was used to estimate the energy dissipation of the proposed design.The proposed technique reduces the occupied space by∼40%,improves cell complexity by∼20%,and reduces energy dissipation by∼1.8 times(atγ=1.5EK)compared to the current scalable designs.This paper also studied the suggested structure’s energy dissipation and compared it to existing works for a better performance evaluation.
基金Project supported by the National Undergraduate Training Projects for Innovation and Entrepreneurship (Grant No. 5003182007)the National Natural Science Foundation of China (Grant No. 12074137)+1 种基金the National Key Research and Development Project of China (Grant No. 2021YFB2801903)the Natural Science Foundation from the Science,Technology,and Innovation Commission of Shenzhen Municipality (Grant No. JCYJ20220530161010023)。
文摘Optical mode converters are essential for enhancing the capacity of optical communication systems. However, fabrication errors restrict the further improvement of conventional mode converters. To address this challenge, we have designed an on-chip TE0–TE1mode converter based on topologically protected waveguide arrays. The simulation results demonstrate that the converter exhibits a mode coupling efficiency of 93.5% near 1550 nm and can tolerate a relative fabrication error of 30%. Our design approach can be extended to enhance the robustness for other integrated photonic devices, beneficial for future development of optical network systems.
文摘Extracellular vesicles(EVs)are membranous vesicular structures released from almost all eukaryotic cell types under different physiological or pathological conditions.Growing evidence demonstrates that EVs can serve as mediators of intercellular communication between donor and recipient cells or microorganism-infected and noninfected cells.Coronavirus disease 2019(COVID-19)disease is caused by infection of the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)of host cells in the respiratory system and various extra-pulmonary tissue/organs,resulting in complications of multiple organ systems.As the cell surface receptor,angiotensin-converting enzyme 2(ACE2)mediates cellular entry of SARS-CoV-2 into the host cells in patients with COVID-19.Recent studies have found that ACE2 can be released with EVs,which have been shown to interfere with the entry of the virus into host cells and thus may be involved in COVID-19 pathophysiology.In addition,ACE2,neprilysin(NEP),and thimet oligopeptidase(TOP)are the key enzymes that regulate angiotensin metabolism by converting angiotensin II or angiotensin I to angiotensin 1-7,the latter of which has protective effects in counterbalancing the harmful effects of angiotensin II in COVID-19 disease.This review summarizes the recent research progress regarding EV-associated ACE2,NEP,and TOP and the perspectives of their potential involvement in the pathophysiology of COVID-19 disease.
基金This work was supported by China Railway Corporation Science and Technology Research and Development Project(P2021J038).
文摘In recent years,switched inductor(SL)technology,switched capacitor(SC)technology,and switched inductor-capacitor(SL-SC)technology have been widely applied to optimize and improve DC-DC boost converters,which can effectively enhance voltage gain and reduce device stress.To address the issue of low output voltage in current renewable energy power generation systems,this study proposes a novel non-isolated cubic high-gain DC-DC converter based on the traditional quadratic DC-DC boost converter by incorporating a SC and a SL-SC unit.Firstly,the proposed converter’s details are elaborated,including its topology structure,operating mode,voltage gain,device stress,and power loss.Subsequently,a comparative analysis is conducted on the voltage gain and device stress between the proposed converter and other high-gain converters.Then,a closed-loop simulation system is constructed to obtain simulation waveforms of various devices and explore the dynamic performance.Finally,an experimental prototype is built,experimental waveforms are obtained,and the experimental dynamic performance and conversion efficiency are analyzed.The theoretical analysis’s correctness is verified through simulation and experimental results.The proposed converter has advantages such as high voltage gain,low device stress,high conversion efficiency,simple control,and wide input voltage range,achieving a good balance between voltage gain,device stress,and power loss.The proposed converter is well-suited for renewable energy systems and holds theoretical significance and practical value in renewable energy applications.It provides an effective solution to the issue of low output voltage in renewable energy power generation systems.
基金funded by the National Natural Science Foundation of China(52067013),and the Provincial Natural Science Foundation of Gansu(20JR5RA395).
文摘In the DC microgrid,the lack of inertia and damping in power electronic converters results in poor stability of DC bus voltage and low inertia of the DC microgrid during fluctuations in load and photovoltaic power.To address this issue,the application of a virtual synchronous generator(VSG)in grid-connected inverters control is referenced and proposes a control strategy called the analogous virtual synchronous generator(AVSG)control strategy for the interface DC/DC converter of the battery in the microgrid.Besides,a flexible parameter adaptive control method is introduced to further enhance the inertial behavior of the AVSG control.Firstly,a theoretical analysis is conducted on the various components of the DC microgrid,the structure of analogous virtual synchronous generator,and the control structure’s main parameters related to the DC microgrid’s inertial behavior.Secondly,the voltage change rate tracking coefficient is introduced to adjust the change of the virtual capacitance and damping coefficient flexibility,which further strengthens the inertia trend of the DC microgrid.Additionally,a small-signal modeling approach is used to analyze the approximate range of the AVSG’s main parameters ensuring system stability.Finally,conduct a simulation analysis by building the model of the DC microgrid system with photovoltaic(PV)and battery energy storage(BES)in MATLAB/Simulink.Simulation results from different scenarios have verified that the AVSG control introduces fixed inertia and damping into the droop control of the battery,resulting in a certain level of inertia enhancement.Furthermore,the additional adaptive control strategy built upon the AVSG control provides better and flexible inertial support for the DC microgrid,further enhances the stability of the DC bus voltage,and has a more positive impact on the battery performance.
文摘In order to predict bifurcation point of the closed-loop current-programmed boost converter and enable this converter to operate at stable parameter space, this paper firstly establishes stroboscopic maps for this converter in the continuous conduction mode according to operating characteristics and topple of this converter. Parameter space at the steady state and bifurcation types are analysed together with stability theory of nonlinear equation. In the solving course, the duty cycle is avoided because of inversive solution, and accuracy is increased. Finally, correction is proved by numerical calculation.
文摘This paper shows DC and small-signal circuit models for the PWM DC to DC buck, boost and back/ boost converters with the equivalent series resistance of the inductor. The DC voltage transfer function and the efficiency of the converter are derived from the DC model. Small-signal open-loop characteristics are derived from the small-signal model based on a state variable model. A design example proves the performance of the circuit and verification of the model.
基金Supported by National Natural Science Foundation of China(Grant No.51575393)
文摘Automotive torque converters have recently been designed with an increasingly narrower profile for the purpose of achieving a smaller axial size and reducing weight. Design of experiment(DOE) and computational fluid dynamics(CFD) techniques are applied to improve the performance of a flat torque converter. Four torque converters with different flatness ratios(0.204, 0.186, 0.172, and 0.158) are designed and simulated first to investigate the effects of flatness ratio on their overall performance, including efficiency, torque ratio, and impeller torque factor. The simulation results show that the overall performance tends to deteriorate as the flatness ratio decreases. Then a parametric study covering six geometric parameters, namely, inlet and outlet angles of impeller, turbine, and stator is carried out. The results demonstrate that the inlet and outlet angles play an important role in determining the performance characteristics of a torque converter. Furthermore, the relative importance of the six design parameters is investigated using DOE method for each response(stall torque ratio and peak efficiency). The turbine outlet angle is found to exert the greatest influence on both responses. After DOE analysis, an optimized design for the flat torque converter geometry is obtained. Compared to the conventional product, the width of the optimized flat torque converter torus is reduced by about 20% while the values of stall torque ratio and peak efficiency are only decreased by 0.4% and 1.7%, respectively.The proposed new optimization strategy based on DOE method together with desirability function approach can be used for performance enhancement in the design process of flat torque converters.
基金supported by the National Natural Science Foundation of China (Grant No.51007068)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No.20100201120028)+1 种基金the Fundamental Research Funds for the Central Universities of Chinathe State Key Laboratory of Electrical Insulation and Power Equipment of China (Grant No.EIPE10303)
文摘In this paper, period-doubling bifurcation in a two-stage power factor correction converter is analyzed by using the method of incremental harmonic balance (IHB) and Floquet theory. A two-stage power factor correction converter typically employs a cascade configuration of a pre-regulator boost power factor correction converter with average current mode control to achieve a near unity power factor and a tightly regulated post-regulator DC-DC Buck converter with voltage feedback control to regulate the output voltage. Based on the assumption that the tightly regulated postregulator DC-DC Buck converter is represented as a constant power sink and some other assumptions, the simplified model of the two-stage power factor correction converter is derived and its approximate periodic solution is calculated by the method of IHB. And then, the stability of the system is investigated by using Floquet theory and the stable boundaries are presented on the selected parameter spaces. Finally, some experimental results are given to confirm the effectiveness of the theoretical analysis.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10247005 and 70571017), the Guangxi New Century Foundation for Ten, Hundred and Thousand Talents (Grant No 2002226).
文摘Based on the mechanism for the generation of chaos in a buck converter, a pole placement method is proposed and applied to controlling the chaos in a circuit. The control circuit is designed and tested. Numerical calculation and circuit implementation demonstrate the validity of this chaos control method.
文摘The so-called Goto's model was modified by introducing a parameter of the oxygen efficiency from industrial trials, as well as the selected and newly re-assessed thermodynamic data. The application of the model to copper converters in Guixi Smelter has been carried out by the combination of thermodynamic calculations with the mass and heat balance using the plant data obtained in industrial trials for many heats. For the slag-making stage, good agreements have been reached betWeen the calculated and measured temperature, blowing time as well as the contents for main elements in the matte and the slag. Relativel}'' large deviations for contents of Zn and Pb in the slag may be caused by the complex chemical composition of the real molten slag, which ma}; result in a large difference of γzn. and γPb,adopted with their real values. It is noted that the model can simulate the slag-making stage of copper converting process in industrial Pierce-Smith converters well.
文摘The measurements and calculations (coupled mode equations) on the conversion of the transverse magnetic TM_(01) vircator (virtual cathode oscillator) mode at 4 GHz to the linearly polarized TE11 mode are presented by means of mode converter systems using a circular waveguide with curvature. The mode converter is composed of the 38.78°bend with 39.07cm curvature and of the 50.78° inverse bend with 25.24cm curvature in the circular waveguide of 9cm internal diameter. The efficiency of conversion from TM_(01) to TE_(11) at 4 GHz exceeds 90%, and the overall etfficiency from TM_(01) to TE_(11) exceeds 90% in the calculated range from 3.72 to 4.8 GHz.
基金supported in part by the National Natural Science Foundation of China under Grant No.61006027the New Century Excellent Talents Program of the Ministry of Education of China under Grant No.NCET-10-0297the Fundamental Research Funds for Central Universities under Grant No.ZYGX2012J003
文摘This paper makes a review of state-of-the- arts designs of successive-approximation register analog-to-digital converters (SAR ADCs). Methods and technique specifications are collected in view of innovative ideas. At the end of this paper, a design example is given to illustrate the procedure to design an SAR ADC. A new method, which extends the width of the internal clock, is also proposed to facilitate different sampling frequencies, which provides more time for the digital-to-analog convert (DAC) and comparator to settle. The 10 bit ADC is simulated in 0.13 μm CMOS process technology. The signal-to-noise and distortion ratio (SNDR) is 54.41 dB at a 10 MHz input with a 50 MS/s sampling rate, and the power is 330 μW.
基金support provided by the Science Foundation Ireland(SFI)under the project High-end computational modeling for wave energy systemsthe Framework Program for Research,Technological Development,and Innovation of the Cyprus Research Promotion Foundation under the Project AΣTI/0308(BE)/05+1 种基金the Irish Research Council for Science Engineering and Technology(IRCSET)Aquamarine Power and by the European Union’s Seventh Framework Programme for research,technological development and demonstration under the grant agreement ASTARTE No.603839
文摘With an increasing emphasis on renewable energy resources, wave power technology is becoming one of the realistic solutions. However, the 2011 tsunami in Japan was a harsh reminder of the ferocity of the ocean. It is known that tsunamis are nearly undetectable in the open ocean but as the wave approaches the shore its energy is compressed, creating large destructive waves. The question posed here is whether an oscillating wave surge converter (OWSC) could withstand the force of an incoming tsunami. Several tools are used to provide an answer: an analytical 3D model developed within the framework of linear theory, a numerical model based on the non-linear shallow water equations and empirical formulas. Numerical results show that run-up and draw-down can be amplified under some circumstances, leading to an OWSC lying on dry ground t
基金Supported by National Natural Science Foundation of China(Grant No.51575393)
文摘With application of the lock-up clutch in the torque converter(TC), fuel economy is not much determined by its high-speed ratio transmission efficiency. As a benefit, more researches are focused on its low-speed ratio performance so as to improve vehicle gradeability and launching acceleration performance. According to the results of computational fluid dynamics(CFD) analysis, hydrodynamic loss inside the stator cascade accounts for 42% of the total energy loss at stalling speed ratio. It is found that upstream flow with large impingement angle results in boundary layer separation at the leading edge, which aggregates hydrodynamic loss and decreases circular flow rate dramatically at low-speed ratio. In this paper, a dual-blade stator is proposed to suppress the boundary layer separation, which is parameterized by using the non-uniform rational B spline(NURBS) method. The mean camber line and blade profile curve are expressed by a three control points quadratic open NURBS and a cubic closed one respectively. The key design parameters included the slot width and suction side shape of the primary blade are analyzed. The most effective slot width is found to be between 4% and 8% chord length, and the boundary layer separation can be suppressed completely by decreasing distribution of momentum moment at the primary blade and adding it to the leading edge of the secondary blade. As a result, circular flow rate and impeller torque capacity is increased by 17.9% and 9.6% respectively at stalling speed ratio, meanwhile, low-speed ratio efficiency is also improved. Maximum efficiency at high-speed ratio decreases by 0.5%, which can be ignored as the work of lock-up clutch. This research focuses on using the dual-blade stator to optimize low-speed ratio performance of the TC, which is benefit to vehicle power performance.